<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        body{
            margin: 10px;
        }
        .box {
            background-color: red;
            position: absolute;
            width: 100%;
            height: 100px;
        }
    </style>
</head>
<body>
<div class="box">
    aa
</div>
<div>bb<br><br><br><br><br><br><br>bb</div>
</body>
</html>